Alex clenched her fists and gritted her teeth.

亚丽克斯握紧拳头，咬紧牙。

《柯林斯英汉双解大词典》

She clenched her fists to stop herself trembling.

她紧握双拳，克制颤抖。

《牛津词典》

Sarah clenched her fists.

握紧她的拳头。

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In South Beach, Staten Island, resident Grace Johnson clenched her fists and waved her arms in the air as she ran toward a college student from Queens who had come to see the damage and stood across the street taking photos.

WSJ: Long Recovery Ahead for Battered Region